1. Field of the Invention
The present invention relates to a remote-controlled camera-picture broadcast system and, more particularly, to a remote-controlled camera-picture broadcast system that facilitates use by a potentially large plurality of unspecified users through a computer network and which is applicable to a video monitoring system.
2. Description of the Prior Art
Conventionally, the remote-controlled camera-picture broadcast systems of this sort have been used to acquire a picture by operating or controlling at least one video camera mounted at a distant place through a computer network.
An example of the conventional remote-controlled camera-picture broadcast systems is disclosed in the Japanese Non-Examined Patent Publication No. 8-265742 published in 1996, which is comprised of a first workstation to which a video camera is connected, a second workstation, a third workstation to which a display monitor is connected, and a fourth workstation to which a display monitor is connected. These four workstations are interconnected together by a network.
Picture transmission/reception software and camera control server software are installed into the first workstation. Camera management server software for managing the video camera is installed into the second workstation. Picture transmission/reception software and camera control client software are installed into the third workstation. Picture transmission/reception software and camera control client software are installed into the fourth workstation.
The camera management server software installed into the second workstation communicates with the camera control server installed into the first workstation to update or renew the state of the video camera connected to the first workstation at any time. Also, the camera management server software notifies regularly the camera control client software installed into the third and fourth workstations of the camera state.
If the user or operator of the third (or fourth) workstation operates the video camera connected to the first workstation, the camera control client software in the third (or fourth) workstation issues a request of access to the camera management server software in the second workstation exclusively managing the camera prior to transmission of a camera operation command. If this request of access is permitted by the camera management server software in the second workstation, the camera management server software transmits a camera operation command directly to the camera control server software in the first workstation to which the video camera is connected. In response to this camera operation command, the picture transmission/reception software in the first workstation transmits the picture information acquired by the video camera directly to the picture transmission/reception software in the third (or fourth) workstation.
If this request of access is not permitted by the camera management server software, the camera management server software transmits a message notifying the refusal of access to the camera control client software in the third (or fourth) workstation.
With the conventional remote-controlled camera-picture broadcast system disclosed in the Japanese Non-Examined Patent Publication No. 8-265742 as described above, however, there are the following three problems.
A first problem is that the cost of the hardware and the network becomes high to ensure or secure the satisfactory performance of the conventional broadcast system even for the use of a lot of unspecified users. The is caused by the following reason.
The use of a lot of unspecified users tends to be concentrated on the camera control server software in the first workstation which is usually mounted on a distant place. Also, the interconnection among the camera control server software, the camera management server software, and the camera control client software need to be always secured for the purpose of the inquiry and notice of the state of the video camera. These facts require the high performance of not only the camera control server software and the first workstation but also the network connected thereto, resulting in high cost of the hardware and the network.
A second problem is that the necessity of maintenance of the camera control server software and the first workstation becomes high in order to ensure the stable operation for a lot of unspecified users. This requires the camera control server software and the first workstation to be located at a place facilitating maintenance, which limits the location of the video camera also.
The second problem is caused by the fact that the camera control server software and the first workstation tend to operate unstably due to load change and/or unjust access since the broadcast system is used by a lot of unspecified users.
A third problem is that the overhead tends to be large on use by a lot of unspecified users, the reason of which is as follows.
If the user of the third workstation operates the video camera, a request for access needs to be transmitted by the camera control client software in the third workstation to the camera management server software in the second workstation in order to acquire the access authority. After the user acquires the access authority, a camera control command is transmitted by the camera management server software in the second workstation to the camera server software in the first workstation according to the access authority, thereby operating the camera connected to the first workstation.
Accordingly, the waiting time for this camera operation from the instruction input by the user to the start of the camera operation tends to be long. Especially, when the transmission speed of the computer network is not high, the waiting time will be longer.
Also, to ensure the camera operation, the holding time of the access authority needs to be set according to the transmission speed of the network. Specifically, the holding time of the access authority needs to be set longer if the transmission speed of the network is low.
Accordingly, an object of the present invention is to provide a remote-controlled camera-picture broadcast system that decreases the cost of hardware and network for the use of a lot of unspecified users.
Another object of the present invention is to provide remote-controlled camera-picture broadcast system that avoids a need for high performance of a camera controller and a network connected thereto.
Still another object of the present invention is to provide a remote-controlled camera-picture broadcast system that decreases the necessity of maintenance of a camera controller located at a distant place.
A further object of the present invention is to provide a remote-controlled camera-picture broadcast system that lowers the overhead even on use by a lot of unspecified users.
The above objects together with others not specifically mentioned will become clear to those skilled in the art from the following description.
A remote-controlled camera-picture broadcast system according to the present invention is comprised of
a camera apparatus for acquiring a picture and producing a video signal of the picture,
a camera controller for controlling the camera apparatus,
a camera server connected to the camera controller through a first network, and
clients connected to the camera server through a second network.
Each of the clients transmits an operation demand for the camera apparatus to the camera server through the second network according to an input of a user.
The camera server receives the operation demand thus transmitted from the client into which the input of the user is applied, and transmits an operation command corresponding to the operation demand thus received to the camera controller through the first network.
The camera controller controls the camera apparatus according to the operation command thus transmitted from the camera server so that the camera apparatus acquires a picture and produces a video signal of the picture.
The camera controller receives the video signal of the picture produced by the camera apparatus, converts the video signal to a picture data, and transmits the picture data to the camera server through the first network.
The camera server transmits the picture data thus received through the second network to the client from which the operation demand has been transmitted, thereby displaying the picture of the picture data on a screen.
With the remote-controlled camera-picture broadcast system according to the present invention, the camera server is connected to the clients through the second network and is connected to the camera controller through the first network. This means that the camera controller is not directly connected to the clients, which is unlike the previously-described conventional remote-controlled camera-picture broadcast system.
Also, the operation demands transmitted from the clients are received by the camera server provided between the clients and the camera controller and then, the operation commands corresponding to the operation demands thus received are transmitted to the camera controller by the camera server as necessary. Thus, there is no possibility that an infinitely increasing load is applied to the camera controller and the first network connected thereto even when the use of a lot of unspecified users is concentrated on this system.
Moreover, since the inquiry about the state of the camera apparatus occurs synchronized with the operation demands transmitted from the clients, there is no need to always or continuously interconnect the camera controller with the camera sever through the first network.
As a result, the camera controller and the first network connected thereto need not have high performance, which decreases the cost of hardware and network for the use of a lot of unspecified users.
Because the camera controller is not directly utilized by the clients, the camera controller does not tend to operate unstably due to load change and/or unjust access even if the broadcast system is used by a lot of unspecified users.
Thus, the necessity of maintenance of the camera controller, which is usually located at a distant place, is decreased.
Further, the access authority is acquired to be synchronized with the transmission of the operation demands transmitted from the clients. Also, the holding time of the access authority is able to be limited within a short period when the camera apparatus is actually operated by the operation commands.
Accordingly, the overhead is lowered even on use by a lot of unspecified users.
In a preferred embodiment of the system according to the present invention, each of the first and second networks is a computer network such as a so-called Local Area Network (LAN).
In another preferred embodiment of the system according to the present invention, the first network is a computer network such as a so-called Local Area Network (LAN) and the second network is the Internet.